TW202107844A - Bonded body and acoustic wave device - Google Patents

Abstract

To provide a bonded body which enables improvement of the Q value of an acoustic wave element. A bonded body 9A according to the present invention is provided with a supporting substrate 6, a piezoelectric material substrate 1A, and a multilayer film 2 that is arranged between the supporting substrate and the piezoelectric material substrate. The multilayer film 2 has a structure wherein first layers 2a having a composition represented by SiOx and second layers 2b composed of a metal oxide are alternately stacked; and x in SiOx is a value larger than 2.

Description

Joint body and elastic wave element

The present invention relates to a joint body of a piezoelectric material substrate and a supporting substrate, and an elastic wave element.

In the past, it has been known to have surface acoustic wave devices that can function as filter elements or oscillators used in mobile phones, Lamb wave elements using piezoelectric films, or thin film resonators (FBAR: Film Bulk Acoustic Resonator). ) And other elastic wave devices. As these elastic wave devices, there is known a device in which a support substrate is bonded to a piezoelectric substrate that propagates a surface acoustic wave, and comb-shaped electrodes that can excite the surface acoustic wave are provided on the surface of the piezoelectric substrate. In this way, by attaching a support substrate with a smaller thermal expansion coefficient than the piezoelectric substrate to the piezoelectric substrate, the dimensional change of the piezoelectric substrate when the temperature changes is suppressed, and the change in the frequency characteristics of the surface acoustic wave device is suppressed .

A known method is to form a silicon oxide film on the surface of the piezoelectric substrate when bonding a piezoelectric substrate and a silicon substrate, and directly bond the piezoelectric substrate and the silicon substrate via the silicon oxide film (Patent Document 1). In this bonding, the surface of the silicon oxide film and the surface of the silicon substrate are irradiated with a plasma beam to activate the surface and perform direct bonding (plasma activation method).

In addition, a direct bonding method of the so-called FAB (Fast Atom Beam) method is known (Patent Document 2). In this method, each bonding surface is irradiated with a neutral atom beam at room temperature to activate each bonding surface, and direct bonding is performed.

In addition, the predecessors proposed a method: between the piezoelectric single crystal substrate and the support substrate, _{an intermediate layer made of Ta 2} O ₅ or the like is provided, and the intermediate layer and the support substrate are irradiated with a neutral beam to make the surface active. It can be bonded directly (Patent Document 3).

Patent Document 4 proposes a structure in which multiple layers of _{SiO 2} layers and Ta ₂ O ₅ layers are stacked between a support substrate and a piezoelectric material substrate. [Related Technical Documents] [Patent Documents]

Patent Document 1: US Patent No. 7213314B2 Patent Document 2: Japanese Patent Application Publication No. 2014-086400 Patent Document 3: WO 2017/163722 A1 Patent Document 4: WO 2018/154950 A1

[Problems to be solved by the present invention]

The elastic wave element of Patent Document 3 has been observed to improve the Q value and other characteristics when it is used for medium frequencies (for 4G at 0.7 to 3.5 GHz, etc.). However, when it is used for high frequencies (for 5G at 3.5-6 GHz, etc.), it is known that the improvement in Q value is small.

In addition, as described in Patent Document 4, _{an elastic wave element in which a multilayer film of SiO 2} /Ta ₂ O ₅ is inserted between a support substrate and a piezoelectric material substrate is reflected from the piezoelectric material substrate by the multilayer film. Support the elastic wave of substrate leakage, and pursue to reduce loss. However, when used for high frequencies (for 5G at 3.5-6 GHz, etc.), it has been found that even for such elastic wave devices, the improvement of the Q value is not necessarily sufficient.

The subject of the present invention is to provide a bonded body that can improve the Q value of an acoustic wave device. [Technical means to solve the problem]

The present invention relates to a bonded body comprising: a support substrate, a piezoelectric material substrate, and a multilayer film between the support substrate and the piezoelectric material substrate. The multilayer film is characterized in that: the multilayer film has SiO _x In the structure where the first layer composed of the composition and the second layer composed of metal oxide are alternately laminated, _x in SiO x has a value greater than 2.

The present invention relates to an elastic wave element, which is characterized by having: The junction body, and An electrode arranged on the piezoelectric material substrate. [Effects of the invention]

The inventor of the present case reviewed that as described in Patent Document 4, _{a multilayer film of SiO 2} /Ta ₂ O ₅ was inserted into the elastic wave element between the support substrate and the piezoelectric material substrate. ~6GHz 5G, etc.), the improvement of the Q factor is not necessarily a sufficient reason. As a result, it is presumed that the quality of the multilayer film suitable for medium frequencies (4G, etc.) is different from the quality of multilayer film suitable for higher frequencies (5G, etc.), and it is difficult to obtain the desired Q value in the high frequency range.

Based on these assumptions, the inventor of the present case considered a method of changing the silicon oxide constituting the first layer of the multilayer film to an oxygen-rich composition, and actually tried out these joints and acoustic wave devices using the joints. As a result, it was found that the Q value was further improved. In particular, it is found that in the high frequency band (5G band), a high Q value can still be obtained, and thus the invention is achieved.

Hereinafter, referring to the drawings as appropriate, the present invention will be described in detail. As shown in Fig. 1(a), the piezoelectric material substrate 1 has a pair of surfaces 1a and 1b. On one surface 1a, a multilayer film 2 is formed. In this example, the multilayer film 2 is obtained by alternately providing the first layer 2a and the second layer 2b on the piezoelectric material substrate 1.

As shown in Fig. 1(b), a bonding layer 4 can be further provided on the surface 3 of the multilayer film 2. In this case, as shown in FIG. 1( c ), the surface of the bonding layer 4 is irradiated with a neutral beam like arrow A, and the surface of the bonding layer 4 can be activated to become the activated surface 5.

On the other hand, as shown in FIG. 2(a), the surface of the support substrate 6 is irradiated with a neutral beam like arrow B to activate the surface of the support substrate 6 to become an activated surface 6a. Next, as shown in FIG. 2(b), the activated surface 5 of the bonding layer 4 and the activated surface 6a of the support substrate 6 are brought into direct contact, and pressure is applied to obtain the bonded body 9 as shown in FIG. 2(b). Arrow C is the junction boundary.

In a preferred embodiment, the surface 1b of the piezoelectric material substrate 1 of the bonded body 9 is further polished, and the thickness of the piezoelectric material substrate 1A is reduced as shown in FIG. 3(a) to obtain the bonded body 9A. 1c is the polished surface. In FIG. 3(b), a predetermined electrode 11 is formed on the polishing surface 1c of the piezoelectric material substrate 1A, thereby fabricating an elastic wave device 10A.

In a preferred embodiment, a bonding layer 14 is also provided on the support substrate 6, and its activated surface 12 is directly bonded to the bonding layer 4 on the multilayer film. Thereby, the joined body 9B as shown in FIG. 4(a) can be obtained. Arrow C shows the joint boundary. As shown in FIG. 4(b), by providing the electrode 11 on the piezoelectric material substrate 1A of this assembly, an acoustic wave element 10B can be obtained.

In addition, in a preferred embodiment, the support substrate and the multilayer film are directly bonded. Thereby, a bonded body 9C as shown in Fig. 5(a) can be obtained. Arrow C shows the joint boundary. As shown in FIG. 5(b), by providing the electrode 11 on the piezoelectric material substrate 1A of this assembly, an acoustic wave element 10C can be obtained.

In the present invention, the multilayer film provided between the support substrate and the piezoelectric material substrate has _{a first layer composed of SiO x} (x greater than 2) and a second layer composed of metal oxide. Laminated structure.

That is, the SiO _x constituting the first layer has an oxygen-rich composition with x larger than 2. By making x larger than 2, when applied to an elastic wave device, the Q value becomes higher. From this point of view, x is preferably 2.03 or more, more preferably 2.05 or more, and further preferably 2.10 or more. In addition, if x exceeds 2.50, the Q value will decrease instead, so it is better to be 2.50 or less, but it is preferably 2.45 or less, and more preferably 2.40 or less.

The metal oxide constituting the second layer is not particularly limited, but it is preferably one or more metal oxides selected from the group consisting of tantalum, hafnium, zirconium, titanium and magnesium, and particularly preferably tantalum oxide and hafnium Oxide, zirconium oxide. The composition of these metal oxides is not particularly limited, but particularly preferably Ta ₂ O _y (4.5≦y≦5), HfO _z and ZrO _z (1.8≦z≦2).

The composition of each layer constituting the multilayer film is measured as follows. Under the conditions for multi-layer film formation, single-layer film formation with a thickness of 150 nm was performed on the Si substrate with the film formation conditions changed. Then, by Rutherford Backscattering Spectrometry (Rutherford Backscattering Spectrometry) method, the RBS spectrum was obtained with Pelletron 3SDH manufactured by National Electrostatics Corporation, and it was calculated from the obtained spectrum by theoretical calculation. In the case of SiOx, it was implemented under the following measurement conditions. Incident ion: ⁴ He ⁺⁺ Incident energy: 2300keV Incident angle: 0deg Scattering angle: 160 and 120deg Sample current: 7nA Beam diameter: 2mmΦ In-plane rotation: No irradiation: 60μC

The method of forming the layers of the multilayer film is not limited, and examples include sputtering, chemical vapor deposition (CVD), and vapor deposition. Here, it is particularly suitable to adjust the amount of oxygen circulating in the chamber when the sputtering target is Si, Ta, Hf, and Zr in reactive sputtering, so that the oxygen ratio of each layer can be controlled.

Specific manufacturing conditions of the respective layers constituting the multilayer film according to the specifications of the chamber, it can be appropriately selected, but the preferred example, the total pressure is 0.28 ~ 0.34Pa, oxygen partial pressure was ^{1.2 × 10 - 3 ~ 5.7 ×} 10 ^{- 2} Pa, the deposition temperature is between room temperature to 200 ℃.

In the present invention, a multilayer film formed by alternately laminating the first layer and the second layer is provided between the piezoelectric material substrate and the supporting substrate. In addition, it is preferable that the number of layers of the first layer and the number of layers of the second layer be two or more respectively. However, even if the number of layers of the first layer and the second layer is too large, the effect will not change significantly. Therefore, from this point of view, the total number of the first layer and the second layer should be 10 or less respectively.

In a preferred embodiment, one or more bonding layers may be provided between the piezoelectric material substrate and the supporting substrate. As the material of these bonding layers, the following materials can be exemplified. Si _{( 1 - v )} O _v , Ta ₂ O ₅ , Al ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ .

Further, in a preferred embodiment, the bonding layer provided between the support substrate and the piezoelectric material substrate has a composition of Si _{( 1 - v )} O _v (0.008≦v≦0.408).

_{Compared with SiO 2} (corresponding to v=0.667), this composition is a composition that considerably reduces the oxygen ratio. By further interposing the bonding layer composed of silicon oxide Si _{( 1 - v )} O _v composed of this, the insulation of the bonding layer can be further improved.

In the composition of Si _{( 1 - v )} O _v constituting each bonding layer, if v is less than 0.008, the resistance of the bonding layer becomes low. Therefore, v is preferably 0.008 or more, more preferably 0.010 or more, particularly preferably 0.020 or more, and even more preferably 0.024 or more. In addition, by setting v to 0.408 or less, the bonding strength is further improved. Therefore, v is preferably 0.408 or less, and more preferably 0.225 or less.

The thickness of each bonding layer is not particularly limited, but from the viewpoint of manufacturing cost, it is preferably 0.01 to 10 μm, and more preferably 0.01 to 0.5 μm.

The film formation method of each bonding layer is not limited, and sputtering, chemical vapor deposition (CVD), and vapor deposition can be exemplified. Here, it is particularly suitable to adjust the amount of oxygen circulating in the chamber when the sputtering target material is Si reactive sputtering, so that the oxygen ratio (v) of each bonding layer can be controlled.

The specific manufacturing conditions of each bonding layer vary depending on the chamber specifications, so it can be selected appropriately, but in a preferred example, the total pressure is 0.28～0.34Pa, and the oxygen partial pressure is 1.2×10 ^{－ 3} ～5.7×10 ^{－ 2} Pa, the film forming temperature is set to normal temperature. In addition, as the Si target, B-doped Si can be exemplified. By EDS, the oxygen concentration of the bonding layer was measured under the following conditions. Measuring device: Elemental analysis is performed using an elemental analysis device (JEOL JEM-ARM200F). Measurement conditions: Observe the thinned sample by FIB (focused ion beam) method at an accelerating voltage of 200kV.

In the present invention, the supporting substrate may be composed of a single crystal or may be composed of a polycrystal. The material of the support substrate should be selected from the group consisting of silicon, SiAlON (silica aluminum oxynitride), sapphire, cordierite, mullite and alumina. The alumina is preferably transparent alumina.

Silicon may be monocrystalline silicon, polycrystalline silicon, or high-resistance silicon.

SiAlON, a ceramic obtained by sintering a mixture of silicon nitride and alumina, has the following composition. Si _{6 - w} Al _w O _w N _{8 - w,} that is, SiAlON, has a composition in which alumina is mixed with silicon nitride, and w represents the mixing ratio of alumina. More preferably, w is 0.5 or more. In addition, w is more preferably 4.0 or less.

Sapphire is a _{single crystal with the composition of Al 2} O ₃ , and alumina is a polycrystal with the composition of _{Al 2} O _3. Cordierite is a ceramic with a composition of _{2MgO·2Al 2} O ₃ ·5SiO _2. The mullite is a ceramic having a composition in the range of _{3Al 2} O ₃ ·2SiO ₂ to 2Al ₂ O ₃ ·SiO _2.

The material of the piezoelectric material substrate is not limited as long as it has the required piezoelectricity, but it is preferably a single crystal _{with the composition of LiAO 3.} Here, A is one or more elements selected from the group consisting of niobium and tantalum. Therefore, LiAO ₃ may be lithium niobate, lithium tantalate, or a lithium niobate-lithium tantalate solid solution.

Hereinafter, each component of the present invention will be further explained. The application of the bonded body of the present invention is not particularly limited, and for example, it can be suitably applied to an elastic wave device or an optical device. As the acoustic wave device, a surface acoustic wave device, a Lamb wave device, a thin film resonator (FBAR), and the like are known. For example, in a surface acoustic wave device, on the surface of a piezoelectric material substrate, an IDT (Interdigital Transducer) electrode (comb-shaped electrode, also called a bamboo curtain electrode) that excites the input side of the surface acoustic wave is provided ), and the IDT electrode on the output side that receives the surface elastic wave. If a high-frequency signal is applied to the IDT electrode on the input side, an electric field is generated between the electrodes to excite the surface acoustic wave and propagate on the piezoelectric material substrate. Then, the propagated surface acoustic wave can be taken out as an electrical signal from the IDT electrode arranged on the output side of the propagation direction.

There may also be a metal film on the bottom surface of the piezoelectric material substrate. The metal film plays a role in increasing the electromechanical coupling coefficient near the back surface of the piezoelectric material substrate when manufacturing the Lamb wave element as an elastic wave device. In this case, the Lamb wave element has comb-shaped electrodes formed on the surface of the piezoelectric material substrate, and has a structure in which the metal film of the piezoelectric material substrate is exposed by the holes provided in the support substrate. As a material of this metal film, aluminum, aluminum alloy, copper, gold, etc. are mentioned, for example. In addition, in the case of manufacturing a Lamb wave element, a composite substrate provided with a piezoelectric material layer without a metal film on the bottom surface can also be used.

In addition, a metal film and an insulating film may also be provided on the bottom surface of the piezoelectric material substrate. The metal film functions as an electrode when manufacturing a thin-film resonator as an elastic wave device. In this case, the thin-film resonator has electrodes formed on the front and back surfaces of the piezoelectric material substrate, and the insulating film is punched to form a structure in which the metal film of the piezoelectric material substrate is exposed. Examples of the material of these metal films include molybdenum, ruthenium, tungsten, chromium, and aluminum. In addition, examples of the material of the insulating film include silicon dioxide, phosphosilicate glass, and borophosphosilicate glass.

In addition, as an optical element, an optical switching element, a wavelength conversion element, and an optical modulation element can be exemplified. In addition, a periodic polarization inversion structure can be formed in the piezoelectric material substrate.

The object of the present invention is an elastic wave device. When the piezoelectric material substrate is made of lithium tantalate, the X-axis, which is the propagation direction of the surface acoustic wave, is used as the center, and the rotation is 123 to 133° from the Y-axis to the Z-axis ( For example, the direction of 128°) is suitable because of its small propagation loss. In addition, when the piezoelectric material substrate is made of lithium niobate, use the X-axis which is the propagation direction of the surface acoustic wave as the center, and the direction rotated 86-94° (for example, 90°) from the Y-axis to the Z-axis, It is suitable because of its small propagation loss. Furthermore, the size of the piezoelectric material substrate is not particularly limited, but, for example, the diameter is 50 to 150 mm and the thickness is 0.2 to 60 μm.

In order to obtain the joined body of the present invention, the following method is preferable. First, the surfaces to be bonded (the surface of the multilayer film, the surface of the bonding layer, the surface of the piezoelectric material substrate, the surface of the support substrate) are flattened to obtain a flat surface. Here, methods for flattening each surface include lap polishing, chemical mechanical polishing (CMP), and the like. In addition, the flat surface is preferably Ra≦1nm, more preferably 0.3nm or less.

Next, in order to remove the residue of the abrasive and the process-deteriorated layer, each surface of each bonding layer is cleaned. The surface cleaning methods include wet cleaning, dry cleaning, brush cleaning, etc. However, in order to obtain a clean surface easily and efficiently, brush cleaning is preferred. At this time, it is particularly suitable to use a mixed solution of acetone and IPA after using SUNWASH LH540 as a cleaning solution by scrubbing a cleaning machine.

Next, by irradiating each bonding surface with a neutral beam, each bonding surface is activated. When performing surface activation by a neutral beam, it is preferable to use a device as described in Patent Document 2 to generate a neutral beam and irradiate it. That is, as the beam source, a saddle field type high-speed atomic beam source is used. Then, an inert gas is introduced into the chamber, and a high voltage is applied to the electrodes from a DC power supply. In this way, the saddle-shaped electric field generated between the electrode (positive electrode) and the frame (negative electrode) moves the electron e to generate a beam of inert gas atoms and ions. The ion beam in the beam reaching the grid is neutralized by the grid, so the beam of neutral atoms is emitted from the high-speed atomic beam source. The atomic species constituting the beam should preferably be an inert gas (argon, nitrogen, etc.). The voltage during activation by beam irradiation is preferably 0.5 to 2.0 kV, and the current is preferably 50 to 200 mA.

Next, in a vacuum atmosphere, the activated joint surfaces are brought into contact with each other to be joined. The temperature at this time is normal temperature, specifically, it is preferably 40°C or lower, and more preferably 30°C or lower. In addition, the temperature at the time of bonding is particularly preferably 20°C or more and 25°C or less. The pressure during joining should preferably be 100 to 20000N. [Example]

(Experiment A) With reference to Figures 1 to 3 and by the method described, try to make a surface acoustic wave device. Specifically, a lithium tantalate substrate (LT substrate) having an OF (Orientation Flat) portion, a diameter of 4 inches and a thickness of 250 μm, is used as the piezoelectric material substrate 1. For the LT substrate, the propagation direction of the surface acoustic wave (SAW) is X, and the cutting angle rotates Y to cut the substrate, that is, 128°Y-cut X-propagation LT substrate. The surface 1a of the piezoelectric material substrate 1 is first mirror polished until the arithmetic average roughness Ra becomes 0.3 nm. And Ra is measured with an atomic force microscope (Atomic Force Microscope, AFM) in a field of view of 10μm×10μm.

Next, on the piezoelectric material substrate 1, the first layer 2 a and the second layer 2 b are alternately formed each of two layers (four layers in total) by a sputtering method to obtain a multilayer film 2. However, the composition of SiOx constituting the first layer was changed as shown in Table 1. The composition of the second layer is hafnium oxide HfO ₂ . The thickness of the first layer and the thickness of the second layer are respectively 150 nm. The film forming methods of the first layer and the second layer are the same as described above. In addition, each composition is adjusted by changing the oxygen ratio in the ambient gas.

Next, on the multilayer film 2, as the bonding layer 4, Si _{( 1 − x )} O _x (x=0.10) (50 nm) is formed. Specifically, the direct current sputtering method is used to use boron-doped Si in the target. In addition, as an oxygen source, oxygen is introduced. At this time, by adjusting the amount of oxygen introduced, the total pressure and oxygen partial pressure of the ambient gas in the chamber are adjusted. The arithmetic average roughness Ra of the surface of the bonding layer 4 is 0.2 to 0.6 nm. Next, the bonding layer 4 is subjected to chemical mechanical polishing so that the film thickness is 80 to 190 nm, and the Ra is 0.08 to 0.4 nm.

On the other hand, as the supporting substrate 6, a supporting substrate 6 made of silicon with a diameter of 4 inches and a thickness of 500 μm having an orientation plane (OF) portion is prepared. The surface of the support substrate 6 is finished by chemical mechanical polishing, and the arithmetic average roughness Ra becomes 0.2 nm.

Next, the surface of the bonding layer 4 and the surface of the Si substrate 6 which is the support substrate 6 are irradiated with a neutral beam to activate the surfaces and directly bond them. Specifically, the surface of the bonding layer 4 and the surface of the support substrate 6 are cleaned, dirt is removed, and then introduced into a vacuum chamber. Evacuated to 10 ^- after ⁶ Pa range, irradiating the surface of the respective fast atom beam (acceleration voltage of 1kV, Ar flow rate 27sccm) 120 seconds. Then, the beam irradiation surface (activation surface) of the bonding layer 4 was brought into contact with the activation surface of the support substrate 6, and then pressed at 10,000 N for 2 minutes to bond them. Next, the obtained bonded body of each example was heated at 100°C for 20 hours.

Next, the surface of the piezoelectric material substrate 1 was ground and polished so that its thickness was changed from 250 μm to 1 μm. Next, an electrode pattern for measurement was formed to obtain a surface acoustic wave device. Then, the Q values at the frequency of 5.5 GHz were measured respectively, as shown in Table 1.

However, the Q value is measured as follows. Fabricate a surface elastic wave resonator on a wafer, and use a network analyzer to measure the frequency characteristics. From the frequency characteristics obtained by this, the resonance frequency _fr and its half-value width Δf _{r are} calculated, and _fr /Δf _{r is} calculated to obtain the Q value.

【Table 1】 O/Si value of SiOx layer Q value evaluation result Comparative example 1 1.88 Benchmark (±0%) Comparative example 2 1.97 ±0% Example 1 2.01 +20% Example 2 2.05 +100% Example 3 2.13 +100% Example 4 2.21 +100% Example 5 2.45 +55% Comparative example 3 2.52 -25%

As shown in Table 1, in Comparative Examples 1 and 2, x=1.88 and 1.97, but all have the same Q value. On the other hand, in Examples 1, 2, 3, 4, and 5, x=2.01, 2.05, 2.13, 2.21, and 2.45 were set, but the Q value was significantly improved compared to Comparative Example 1. In Comparative Example 3, x=2.52, but compared with Comparative Example 1, the Q value deteriorated. In this case, it is considered that the film density is reduced.

(Experiment B) In experiment A, the material of the second layer was changed from hafnium oxide to tantalum oxide Ta ₂ O ₅ . Make the material of the first layer, the composition of SiOx, the same as experiment A. Then, after measuring the Q value of the obtained element, the same result as experiment A was obtained.

(Experiment C) In experiment A, the material of the second layer was changed from hafnium oxide to zirconium oxide (ZrO ₂ ). Make the material of the first layer, the composition of SiOx, the same as experiment A. Then, after measuring the Q value of the obtained element, the same result as experiment A was obtained.

1,1A: Piezoelectric material substrate 1a, 1b, 3: surface 1c: Grinding surface 2: Multilayer film 2a: first layer 2b: second layer 4, 14: Bonding layer 6: Support substrate 5, 6a, 12: activated surface 9, 9A, 9B, 9C: joint body 10A, 10B, 10C: elastic wave components 11: Electrode A, B: Neutral beam C: Joint boundary

Fig. 1(a) shows the state where the multilayer film 2 is provided on the piezoelectric material substrate 1, Fig. 1(b) shows the state where the bonding layer 4 is provided on the multilayer film 2, and Fig. 1(c) shows the bonding layer 4 The state of surface activation. Fig. 2(a) shows the state in which the surface of the support substrate 6 is activated, and Fig. 2(b) shows the assembly 9 of the support substrate and the piezoelectric material substrate. FIG. 3(a) shows a state where the piezoelectric material substrate 1A of the bonded body 9A is processed to make it thinner, and FIG. 3(b) shows a state where electrodes are provided in the bonded body 9A. Fig. 4(a) shows the bonded body 9B obtained by directly bonding the bonding layer 4 provided on the multilayer film and the bonding layer 14 provided on the support substrate 6, and Fig. 4(b) shows the piezoelectric of the bonded body 9B The elastic wave element 10B obtained by providing the electrode 11 on the flexible material substrate 1A. Fig. 5(a) shows the bonded body 9C obtained by directly bonding the multilayer film 2 and the support substrate 6, and Fig. 5(b) shows a state where electrodes are provided on the piezoelectric material substrate 1A of the bonded body 9C.

1A: Piezoelectric material substrate

1a: surface

1c: Grinding surface

2: Multilayer film

2a: first layer

2b: second layer

4: Bonding layer

6: Support substrate

5, 6a: activated surface

9A: Joint

10A: Elastic wave element

11: Electrode

C: Joint boundary

Claims (8)

A joint body, comprising: a support substrate, a piezoelectric material substrate, and a multilayer film between the support substrate and the piezoelectric material substrate, characterized in that: the multilayer film has a first composition _{having SiO x} A structure of alternately stacked layers and a second layer made of metal oxide, wherein _x in the SiO x has a value greater than 2. Such as the joint body of the first item of the claim, in which, In the first layer, x satisfies 2.03≦x≦2.50. Such as the joint body of claim 1 or 2, in which, The metal oxide is selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide. Such as the joint body of claim 1 or 2, in which, The thickness of the first layer and the thickness of the second layer are respectively 20 nm or more and 500 nm or less. Such as the joint body of claim 1 or 2, in which, The multilayer film includes two or more layers each including the first layer and the second layer. The bonded body of claim 1 or 2, wherein, between the piezoelectric material substrate and the supporting substrate, _{a bonding layer having a composition of Si ( 1 - v )} O _v (0.008≦v≦0.408) is included . An elastic wave component, which is characterized by including: Such as the joint body of any one of items 1 to 6 of the claim, and An electrode arranged on the piezoelectric material substrate. For example, the elastic wave element of claim 7 is for elastic waves with a frequency of 3.5 to 6 GHz.

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